Incandescent lamp filament supports

ABSTRACT

Incandescent lamps such as vehicle lamps, projector or general lighting lamps have their internal components including one or more filaments supported within their envelopes on a plurality of sheet metal fingers through which current is supplied to the filament(s). The lamps can be made from a metal sheet provided with a series of fingers which are all interconnected at their roots by a portion of the sheet; after affixing internal components of the lamp to selected fingers and securing the fingers together, for example by an insulating bridge, the interconnecting portion is severed from the fingers thereby physically isolating the fingers from one another.

United States Patent [1 1 Vause 1 INCANDESCENT LAMP FILAMENT- SUPPORTS ['13] tmemm: Arthur Samuel Vause, London,

England [73] Assignee: Thorn Electrical Industries Limited,

London, England [22] Filed: Apr. 19, 1971 [21] Appl. No.2 135,002

[30] Foreign Application Priority Data Nov. 20, 1973 Primary Examiner-John K. Corbin Attorney-Joseph C. Ryan and Robert F. O'Connell [57 ABSTRACT Incandescent lamps such as vehicle lamps, projector or general lighting lamps have their internal components including one or more filaments supported within their envelopes on a plurality of sheet metal fingers through which current is supplied to the filament(s). The lamps can be made from a metal sheet provided with a series of fingers which are all interconnected at their roots by a portion of the sheet; after affixing internal components of the lamp to selected fingers and securing the fingers together, for example by an insulating bridge, the interconnecting portion is severed from the fingers thereby physically isolating the fingers from one another.

11 Claims, 12 Drawing Figures PAIENIEDHHYZOIBYS 3.774.064 SHIT 1 CF 3 'f PRIOR ART I 27 AF+- H u 2/ 26 28 1 9, ARTHUR SAMUEL VAUSE INVENTOR BY 6/41,

U ATTORNEY PATENTED R9! 2 01975 ARTHUR SAMU EL VAUSE INVENTOR BY wfv ATTORNEY PAIENTED um 20 I975 ARTHUR SAMUEL VAUSE C/ ATTORNEY INCANDESCENT LAMP F ILAMENT SUPPORTS The present invention relates to the manufacture of incandescent lamps.

In manufacturing incandescent lamps in the past it has been customary to mount the internal components of the lamps on supporting wires and a typical lamp is shown in FIG. 1 of the accompanying drawings.

It will be seen from FIG. 1 that the lamp has a sealed light-transmitting envelope enclosing a pair of filaments 1!, l2 and a shield or reflector 13. The filaments ll, 12 and the reflector 13 are affixed to three bent wires 14 of circular cross-section and the two filaments are each connected across a different two of the three wires 14 so that current can be supplied to each filament independently of the other. The three wires 14 have lead-in conductors 15 including metal foils 16 attached thereto and the metal foils 16 are held in a pinch seal located where indicated at 17. The set of wires 14 are frequently embedded within insulating bridges of materials such as glass, fuzed silica or quartz for convenience of construction and for robustness. An insulating bridge is shown in FIG. 1 at 18. The filaments 11, 12 and reflector 13 may be secured to the wires 14 by mechanical means, for example by clamping or crimping or by welding.

In order to prevent substantial variations in electrical, photometric and life behaviour characteristics from lamp to lamp, it is necessary that the various stages in their constructionbe precisely controlled, and the internal components must be precisely located relative to each other. The construction should be robust so that the lamps can withstand mechanical shock in handling and service. The more internal components, the more difficult it is to ensure that desired robustness, precision in assembly and uniformity of performance will be achieved.

Owing to the several difficulties and disadvantages met with during the construction of lamps similar to the one shown in FIG. I particularly where many components have to be assembled with precision, complex jigs may be required for locating and holding the components during assembly. The design and fabrication of such jigs can be very costly. The use of wires of circular cross-section adds to the difficulty of precision manufacture, even when jigs are employed. There is the likelihood that such a wire will be displaced while securing a component thereto. Thus it is difficult to prevent the wire from rolling or twisting when force is applied during the securing operation, which may for example consist of clamping or welding. Furthermore, the wires have to be bent to relatively complex shapes in order to set the position of the various components relative to one another and accurate positioning is difficult to achieve and maintain during assembly.

Junctions between a support wire of circular crosssection and a filament wire also of circular crosssection afford minimal surface contact between the wires. A welded junction between the wires can lack strength because of inadequate flow of one metal into the other. Moreover electrical resistance through the junction can be high and this can produce excessive local heating when lamps similar to that illustrated in FIG. I are used. This local heating can impair the strength of the weld and result in a fragile lamp that could readily be destroyed by vibration or shock. This problem is particularly severe where refractory metals are used in the lamp and this applies in connection with tungsten-halogen lamps.

A still further disadvantage of lamps utilising support wires of circular cross-section is the occurrence of multiple unwanted reflections off the wires when the lamp is in use.

In accordance with the present invention, there is provided an incandescent lamp in which internal components thereof including a filament are supported within the envelope of the lamp on a plurality of sheet metal fingers. The invention is applicable to incandescent lamps which are evacuated or which include a filling of gas or of a gaseous mixture, and may be applied to such lamps as metal-halogen lamps. Lamps which may incorporate the features of the invention may be used for any application, for example, domestic lighting service, projection and studio use and for transport lighting. The invention is also applicable to flash lights, sub-miniature and micro-miniature lamps. In one embodiment, the lamp can include two filaments arranged so that they can be independently supplied with current, thereby being suitable for use as in a vehicle headlamp or stop/tail lamp, for example. In another embodiment, the lamp can be in the form of a monoplane fila ment projection lamp having a grid filament arranged in a zig-zag path between supporting fingers. The lamps can be constructed, according to the invention by a method in which a support for the internal components of the lamp is made from a metallic sheet, the support including a plurality of fingers that are interconnected by a portion of sheet bridging their roots, securing the ends of a filament between two of the fingers remote from their roots so as to effect electrical connection therewith, affixing the fingers, remote from their fingertips, to an insulating mount which holds the fingers in fixed positions relative to one another and removing the bridging portion of sheet to isolate the fingers from each other.

The use of a sheet for making the support simplifies location of the various components relative to one another, makes it possible to dispense with complex jigs, and facilitates the construction of a robust lamp which is more resistant to mechanical shocks than conventionally-construeted lamps. Troublesome multiple reflections frequently observed when conventional lamps are operated can be substantially reduced by appropriate disposition of the planes of the sheet metal fingers relative to the filament axes. The sheet support may include engagement means such as tangs for engagement with the inner surface of the lamp envelope, and the latter may have a contoured inner surface to cooperate with the engagement means. Positive location of the internal components may therefore be achieved resulting in a particularly robust lamp.

The invention will now be described in more detail with reference to the remaining figures of the accompanying drawings, in which:

FIGS. 2 to 4 illustrate stages in the manufacture of a twin-filament lamp,

FIG. 5 illustrates a completed twin-filament lamp, and

FIG. 6 to 8 illustrate the manufacture of a monoplane filament projector lamp, shown per se in FIG. 8,

FIGS. 9 and 10 illustrate an automobile stop-tail lamp,

FIG. 11 illustrates a general lighting service lamp, and

FIG. 12 is a detail illustrating a fuse arrangement that may be incorporated in a lamp.

A twin-filament lamp as illustrated in FIG. is intended for use on vehicles and enables main and dipped beams to be projected depending on which filament is fed with current. It may, for example, be a tungsten halogen lamp.

To make such a lamp, a support for the internal components including the filaments which are to be contained within an envelope is made from a metallic sheet consisting of a refractory metal such as tungsten, molybdenum or alloys containing these metals. The metallic sheet can alternatively consist of a metal or alloy whose characteristic expansion is matched with the particular vitreous material from which the envelope is made. Thus, if the envelope is made from a hard glass such as alumina or borosilicates, Fernico, an ironnickel cobalt alloy may be used. If the envelope is made from a soft glass such as lime soda or lead, Nilo, a nickel iron alloy or similar may be used. Areas are cut out of the sheet so as to form three fingers, which extend away from a bridging portion of sheet 21 interconnecting the fingers at their roots. Methods of cutting the sheet can include mechanical methods, for example stamping, chemical or electrolytic etching, or spark or laser-beam erosion. The lengths of the fingers are dissimilar and, as shown in FIG. 2, one finger has an extension 22 attached thereto by mechanical means such as crimping. The extension 22 is provided with a flange 23 to which a shield or reflector is later attached.

After cutting the sheet, the fingers thus formed are bent to define tangs 24 located at the fingertips. A further tang 25 is provided at the junction between the extension 22 and its associated finger.

A shield or reflector 26 is next attached to the flange 23 of the extension 22, for example by welding. The reflector 26 is a bowl, and as may be seen in FIGS. 3, 4 and 5, it will reflect a light beam generated by a filament in a direction parallel to the planes containing the fingers. In other words, the fingers 20 are positioned edgewise to the beam reflected by the reflector 26 when the lamp is operated. This arrangement is particularly advantageous, because it keeps extraneous multiple reflections to a minimum. Instead of making the shield or reflector 26 as a separate piece attached to the extension 22, it could be made an integral part of the metallic sheet. Such an integrally-formed shield or reflector 26 may be produced by pressing or cupping, or rolling a portion of the metallic sheet. In the lamp illustrated in FIG. 5, the shield or reflector 26 could, for instance, be integral with the extension 22.

Two tungsten filaments 27 and 28 are now secured to the fingers 20 so as to effect electrical connections therewith and to be capable of being independently supplied with current. The ends of the filaments 27, 28 are secured to the fingers 20 by trapping and pinching them between the tangs 24, 25 and the respective finger. Thus the ends of the filament 27 associated with the reflector 26 are secured with the tang 24 provided on the extension 22 of one finger and with the tang 24 of one of the other fingers. Similarly, the ends of the filament 28 are secured to the tang 25 of the firstmentioned finger and to the remaining other finger. In this way, the two filaments 27 and 28 are connected between a different two of the three fingers, and both filaments are electrically connected to a common finger at one of their ends.

An insulating bridge 29 is affixed across each of the fingers 20 by embedding the fingers therein. The insulating bridge 29 may be of glass, fuzed silica or quartz, or other ceramic material, and it stiffens the support and maintains the fingers 20 in their designed relative positions. The insulating bridge 29 is located intermediate the roots and tips of the fingers 20, and the fingers 20 extend through the bridge 29 with their roots spaced therefrom. It will be appreciated that a separate insulating bridge member need not be provided; in G.L.S. lamps for example, the functions of this member may be accomplished simply by embedding the fingers in the base part of the envelope.

The bridging portion of sheet 21 is then removed by severing along the line 30 shown in FIG. 4. The fingers are thereby electrically and physically isolated from one another.

The twin-filament lamp is finally completed by welding lead-in conductors to each of the fingers 20 and sealing the complete assembly 31 into a lighttransmitting envelope 32. In doing so, the ends 33 of the fingers protruding from the insulating bridge are sealed through a base part of the envelope 32 by means of a pinch seal located at A. The lead-in conductors consist of pins 35 and refractory metal strips 36, and the envelope 32 may be of glass or quartz. For good sealing with quartz, the strips 36 should consist of molybdenum.

The lamp can be completed in another, simpler manner which eliminates the necessity of having welded joints, that may prove troublesome within the pinch seal A. The metal sheet forming the starting point in the making of the lamp is made longer so that the roots of the fingers 20 are spaced further from the bridge 29 seen in FIG. 4. By an appropriate increase in length, it may be arranged that the bridging portionof sheet 21 lies instead outside the pinch seal shown at A in FIG. 5. After pinch sealing about the portions of the fingers 20 intermediate the bridge 19 and the bridging portion of sheet 21, the latter portion 21 is removed. It may be convenient to deform these intermediate portions of the fingers 20 to provide rolled-foil sections for embedding in the pinch seal at A. Where the lamp is of the metal-halogen type, the metallic sheet may be molybdenum or a molybdenum-rhenium alloy, provided with a rolled-foil section for embedding in the pinch seal at A of the envelope 32. The envelope 32 is made of quartz in this case. If the envelope 32 of the lamp, whether conventional or halogen-type, is of hard glass (alumina or borosilicate), the metallic sheet can be Fernico alloy and if the envelope 32 is of soft glass (lime soda or lead glass), Nilo 475 alloy is suitable. The provision of rolled-foil sections is optional in the latter two examples. The alternative construction just described is particularly attractive because it is not until after sealing the assembled internal components of the lamp into the envelope 32 that the bridging portion of sheet 21 is removed. The resulting strength and stiffness conferred to the assembly, by so retaining the said portion of sheet 2H minimises damage thereto during handling and process transfer during manufacture.

A method of making a monoplane-filament projection lamp, which may be a tungsten-halogen type, is illustrated in FIGS. 6 to 8, and in these drawings parts similar to those illustrated in the preceding drawings have been given primed references.

In this method, a metallic sheet has areas removed so as to leave a support having two arrays of fingers 14 and 14" which are disposed between lateral sheet portions 37. The latter portions 37 are to form fingers to whichthe ends of a grid filament 38 are to be secured. The two arrays of fingers l4 and 14", which respectively contain five and four fingers, lie in a common plane and point towards each other with the fingertips of one array spaced longitudinally from the fingertips of the other array. Tangs 24' are provided at the ends of the fingertips l4 and 14" and a coil filament 38 is disposed in a zig-zag path between the fingertips of 14 and 14", the filament being passed over the tangs 24. The ends of the filament 38 are secured to the portions 37 by tangs, not visible in the drawings, although they could be secured by welding. After affixing insulating bridges 29' across the fingers, the bridging portions of sheet 21' are removed by severing along the lines 30' and the fingers formed from the lateral portions 37 are provided with lead-in conductors comprised of pins 35' and foils 36'. It will be seen that a reflector 26' has an extension or leg 39 and is secured with the support by embedding the leg 39 in one of the insulating bridges 29. It will further be seen that the individual fingers of each of the two arrays 14' and 14" are isolated from one another when the bridging portions of sheet 21 are removed.

An automobile stop/tail light 40 is shown in FIG. 9 and FIG. 10, FIG. illustrating the lamp shown in FIG. 9 as seen from the left thereof. The light 40 includes two filaments 41, 42, and each end of the filaments is clamped to the tip of a separate finger 43, 44 of the metallic support sheet. The fingers 43 are bent so that their tips lie in a plane spaced from the plane in which lie the tips of the fingers 44. There are four fingers, of which one pair, that seen at the right in FIG. 9, are electrically and mechanically connected whereas the fingers of the other pair are isolated from each other. With this arrangement, current can be supplied to each filament independently of the other. The fingers are all embedded in a support bridge 46 and they extend through a pinch seal base or wedge-base 47 of the envelope 48. As will be seen, the base of the lamp has an exhaust tube 49 sealed therein, which is closed off after exhausting and/or filling the envelope 48. The bridging portion of sheet 21 is arranged to clear that part of the exhaust tube 49 that is removed after closing, and that is shown dotted. After exhausting and sealing off the envelope by closing the tube 49, the bridging portion of sheet 21 is removed by cutting along the line 30.

Although the tips of the fingers 43, 44 of each pair of fingers are shown in FIG. 9 to be laterally displaced from one another, it may be preferred to locate them in line with each other,'with their finger tips lying in different planes.

A general lighting service lamp is shown in FIG. 11, and may have a pinch-seal or wedge base construction 51. The base includes an exhaust tube 52 similar to the arrangement shown in FIGS. 9 and 10. The lamp 50 has a single filament that is attached at its ends to two fingers 52, along which current is supplied in use, and is additionally supported by two fingers 53. The fingers 53 branch from the fingers 52 but are separated from the latter after an insulating bridge 54 has been affixed across the fingers, portions 56 being then removed.

The filament 57 can be mono-plane, in which case the fingers all lie in the same plane. However, it may be preferred to locate the fingers 53 in a different planespaced from the plane containing the fingers 52.

Finally, the metallic support can be readily arranged to include a fuse link, which may be located either within the lamp envelope, thus eliminating the need for locating them within a lamp cap or externally of the lamp. FIG. 12 illustrates how a fuse-link 60 may be incorporated within a lamp envelope. The metallic sheet includes an open, rectangular framework 62 and an insulating bridge 63 is attached across the framework 62. The dotted portion 64 is removed, to leave a leg 65 and fingers 68 and dotted portion 66 is removed leaving a leg 67 and a separate finger 69. The fuse link 60 is then connected and clamped across the legs 65 and 67. In use therefore, current passes along the finger 68, through the fuse link 60 and thence to the finger 69.

I claim:

1. An improved incandescent lamp of the regenerative, tungsten-halogen type comprising an hermetically-sealed tubular envelope having a pinch seal at one end thereof;

a plurality of internal lamp components inside said envelope at least one of said components being a tungsten filament,

supporting means within said envelope to carry said components and maintain them in predetermined relative positions, said supporting means comprising a plurality of elongated sheet metal fingers;

' an insulating bridge inside said envelope and separate therefrom said fingers being embedded intermediate their ends within the body of said insulating bridge whereby said fingers are held alongside one another in fixed relative positions, the embedded parts of said fingers lying in a common plane;

the ends of said filament being secured and electrically connected to a pair of said fingers, said pair of fingers having attachment means for said filament ends, said attachment means comprising tangs on said fingers, and said filament ends being gripped between said tangs and the parts of said fingers adjacent said tangs; and

said pair of fingers are adapted for electrical connection to an electrical supply.

2. A lamp according to claim 1, including a reflector that is in fixed relationship with the arrangement of sheet metal fingers.

3. A lamp according to claim 2, wherein said reflector is affixed to at least one of said fingers.

4. A lamp according to claim 2, wherein said reflector is oriented to reflect light emitted by the filament, in a direction substantially parallel to a plane in which said fingers lie.

5. A lamp according to claim 1, further including a reflector, said reflector having an extension which is secured to said insulating mount to hold said sheild or reflector in fixed relation to said fingers.

6. A lamp according to claim 1 having two filaments, the ends of said filaments being secured to separate fingers whereby each filament can be independently supplied with current.

7. A lamp according to claim 6, having three fingers, one end of each filament being secured to a first of said fingers; the opposite end of one filament being secured to a second finger; and the opposite end of the other filament being secured to the remaining finger.

8. A lamp according to claim 1, including: a grid filament, two arrays of parallel sheet metal fingers, the fingets in one array pointing towards the fingers in the other array with their fingertips spaced apart from the fingertips of the fingers in the other array, the fingers in each array being isolated from one another and said grid filament being supported by the fingers of the said two arrays.

9. A lamp according to claim 8, wherein the ends of said grid filament are secured to two separate fingers located at either side of said two arrays, said fingertips of said fingers in said two arrays having tangs and said filament being disposed in a zig-azg path from tang-totang.

10. A lamp according to claim 1 and further including lead-in conductors accessible from the exterior of the envelope and connected to said pair of fingers for connecting said pair of fingers to said electrical supply.

11. A lamp according to claim 1, wherein the metal comprising said fingers is arefractory metal. 

1. An improved incandescent lamp of the regenerative, tungstenhalogen type comprising an hermetically-sealed tubular envelope having a pinch seal at one end thereof; a plurality of internal lamp components inside said envelope at least one of said components being a tungsten filament, supporting means within said envelope to carry said components and maintain them in predetermined relative positions, said supporting means comprising a plurality of elongated sheet metal fingers; an insulating bridge inside said envelope and separate therefrom said fingers being embedded intermediate their ends within the body of said insulating bridge whereby said fingers are held alongside one another in fixed relative positions, the embedded parts of said fingers lying in a common plane; the ends of said filament being secured and electrically connected to a pair of said fingers, said pair of fingers having attachment means for said filament ends, said attachment means comprising tangs on said fingers, and said filament ends being gripped between said tangs and the parts of said fingers adjacent said tangs; and said pair of fingers are adapted for electrical connection to an electrical supply.
 2. A lamp according to claim 1, including a reflector that is in fixed relationship with the arrangement of sheet metal fingers.
 3. A lamp according to claim 2, wherein said reflector is affixed to at least one of said fingers.
 4. A lamp according to claim 2, wherein said reflector is oriented to reflect light emitted by the filament, in a direction substantially parallel to a plane in which said fingers lie.
 5. A lamp according to claim 1, further including a reflector, said reflector having an extension which is secured to said insulating mount to hold said sheild or reflector in fixed relation to said fingers.
 6. A lamp according to claim 1 having two filaments, the ends of said filaments being secured to separate fingers whereby each filament can be independently supplied with current.
 7. A lamp according to claim 6, having three fingers, one end of each filament being secured to a first of said fingers; the opposite end of one filament being secured to a second finger; and the opposite end of the other filament being secured to the remaining finger.
 8. A lamp according to claim 1, including: a grid filament, two arrays of parallel sheet metal fingers, the fingers in one array pointing towards the fingers in the other array with their fingertips spaced apart from the fingertips of the fingers in the other array, the fingers in each array being isolated from one another and said grid filament being supported by the fingers of the said two arrays.
 9. A lamp according to claim 8, wherein the ends of said grid filament are secured to two separate fingers located at either side of said two arrays, said fingertips of said fingers in said two arrays having tangs and said filament being disposed in a zig-azg path from tang-to-tang.
 10. A lamp according to claim 1 and further including lead-in conductors accessible from the exterior of the envelope and connected to said pair of fingers for connecting said pair of fingers to said electrical supply.
 11. A lamp according to claim 1, wherein the metal comprising said fingers is a refractory metal. 